The purpose of the study is to perform preliminary experiments to identify a serologic marker for a putative viral agent associated with Kaposi's sarcoma (KS) and to isolate the putative virus from patient specimens. The purpose of the current investigation is to develop serologic markers of infection with KSHV (Kaposi's sarcoma associated herpesvirus) and to isolate infectious virus. In preliminay studies we have identified a protein antigen, p40, which is recognized by the sera of approximately 70% of AIDS patients with KS. Further studies are required to define in larger population groups the sensitivity and specificity of this marker. Untimately, the study of this virus will be greatly enhanced if it can be isolated and grown in culture.